The use of enzymes and organisms can improve or enhance the performance of animals and the value of the feed the animals receive. For example, WO-A-9210945 discloses such a combination for use in enhancing the value of prepared silage, and WO-A-9617525 relates to enhancement of animal performance using microorganisms. The efficacy of combining the use of enzymes together with organisms producing volatile fatty acids (VFA's) is also described. In this case, better preservation of the silage, better animal performance and a reduction in effluent production were demonstrated. WO-A-9503396 demonstrates that some advantages may accrue when a desired VFA profile is produced during the silage fermentation; it has also been found that this does not produce the desired reduction in heating, on opening the silage clamp.
The production of silage and the associated crop husbandry have over recent years developed to an extent that a number of different processes can be defined. These are: (i) the ensiling of young grass with particularly low dry matter, e.g. less than 25% (common in UK, Ireland and Scandinavia), (ii) the ensiling of higher dry matter, more mature grasses (UK), the ensiling of high dry matter but young grass achieved by wilting (Netherlands); and (iii) the ensiling of whole maize including stova and cob, usually at a dry matter concentration of about 35%, and whole crop cereals, e.g. wheat, at 45-50% dry matter.
Particularly in cases (ii) and (iii), one major problem occurs on a regular basis. This is the phenomenon known as aerobic spoilage. This phenomenon is not well understood. Although there are many differing opinions, the process of aerobic spoilage can be divided into phases. Thus, there is an initial phase in which yeasts and sometimes acetic acid bacteria start to respire the preserving organic acids. After an initial rise in pH, there is a secondary phase in which the activity of bacilli is apparent, and is associated with increasing temperature. A further phase includes activity of various microorganisms including fungi.
In those silages which contain a substantial content of dry matter, i.e. over 30%, the problem of spoilage is particularly acute. Spoilage is seen to a greater or lesser extent once a silage clamp is opened and exposed to air.